Revisiting imidazolium receptors for the recognition of anions: highlighted research during 2010-2019

Imidazolium based receptors selectively recognize anions, and have received more and more attention. In 2006 and 2010, we reviewed the mechanism and progress of imidazolium salt recognition of anions, respectively. In the past ten years, new developments have emerged in this area, including some new imidazolium motifs and the identification of a wider variety of biological anions. In this review, we discuss the progress of imidazolium receptors for the recognition of anions in the period of 2010-2019 and highlight the trends in this area. We first classify receptors based on motifs, including some newly emerging receptors, as well as new advances in existing receptor types at this stage. Then we discuss separately according to the types of anions, including ATP, GTP, DNA and RNA.

Imidazolium Based Probes for Recognition of Biologically and Medically Relevant Anions

The imidazolium derivatives due to their positive charge possess one of the most polarized and positively charged proton at C2-H to form strong ionic hydrogen bond (also termed as double ionic hydrogen bond) with anions and also provide opportunities for anion - π interactions with electron-deficient imidazolium ring. In the present review article, imidazolium based molecular probes for their ability to recognize inorganic anions like halides, cyanide, perchlorate, carboxylic acids, phosphate, sulfate etc. and their derived molecules viz. nucleotides, DNA, RNA, surfactants, proteins, etc have been discussed. The review covers the literature published after year 2009 and has > 130 references. The previous literature has already been discussed by Yoon et al. in two review articles published in Chem. Soc. Rev. 2006 and 2010.

Ratiometric fluorophore for quantification of iodide under physiological conditions: applications in urine analysis and live cell imaging

The ratio of fluorescence intensity of fluorophoreI_{395 nm}/I_{475 nm}vs.log [I⁻] undergoes linear change over a broad iodide concentration range of 10⁻⁹to 10⁻⁵M and finds application in urine analysis and live cell imaging.

Highly precise detection, discrimination, and removal of anionic surfactants over the full pH range via cationic conjugated polymer: an efficient strategy to facilitate illicit-drug analysis

A water-soluble cationic conjugated polyelectrolyte (CPE), poly(1,4-bis(6-(1-methylimidazolium)-hexyloxy)-benzene bromide) (PMI) displays extraordinary stability over the full pH range of 1-14 as well as in seawater, brine, urine, and other solutions and carries out efficient detection, discrimination, and removal of moderately dissimilar anionic surfactants (viz., sodium dodecyl benzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS)) at very low levels (31.7 and 17.3 parts per billion (ppb), respectively). PMI formed stable hydrogels in the presence of SDS that remained unaffected by strong acids/bases, heating, ultrasonication, or exposure to light, whereas SDBS formed precipitate with PMI as a result of its different interpolymer cofacial arrangement via Columbic attraction. The complex-forming ability of PMI with SDS and SDBS facilitated their elimination from water or drug-doped urine samples without the use of any organic solvent, chromatographic technique, or solid support. This protocol, the first of its kind for the removal of anionic surfactants at very low concentrations from any type of solution and competitive environments, demonstrates an original application using a CPE. The surfactant-free sample solutions could be precisely analyzed for the presence of illicit drugs by any standard methods. Using PMI, a newly developed CPE, a rapid and practical method for the efficient detection, discrimination, and removal of SDS and SDBS at ppb levels from water and urine, under harsh conditions, and in natural chemical environments is demonstrated.

Quantitative and highly selective sensing of sodium houttuyfonate via long-aliphatic chains hydrophobic assembly and aggregation-induced emission

An α-cyanostilbene derivative was synthesized for the selective detection of sodium houttuyfonate via AIEE with an obvious fluorescence enhancement.